Water reducing agents are widely used with the aim of improving the quality of cement compositions such as concrete, mortar, etc. Naphthalenesulfonate-formalin condensates, melaminesulfonate-formalin condensates, ligninsulfonates, polycarboxylic acids, etc. are generally used as water reducing agents. Among these, the demand for polycarboxylic acid type water reducing agents, developed in recent years, is continually increasing because they have better water reducing properties than other water reducing agents.
When looking at developments up to this day, polycarboxylic acid type water reducing agents can be roughly divided into dispersion type water reducing agents which aim at the water reducing effect and slump maintaining type water reducing agents which aim at preventing slump loss.
In the early days of polycarboxylic acid type water reducing agent development, when the attention was on the dispersion type water reducing agents, the use of copolymers of unsaturated dicarboxylic acids or unsaturated monocarboxylic acids not having a polyalkylene-oxide group etc. has been proposed (refer for example to Documents 1 and 2). However, the slump loss preventing properties of these agents are of course insufficient, and even their water reducing properties are inadequate. Thereafter, polycarboxylic acid type water reducing agents for cement which have a polyalkylene oxide group and improved water reducing properties such as copolymers of polyethylene glycol methacrylate and methacrylic acid (refer for example to Document 3) and copolymers of polyethylene glycol methacrylate, methacrylic acid and amide compound adducts having polyalkylene oxides of unsaturated carboxylic acid (refer for example to Document 4) etc. were developed and widely used instead of those mentioned above. However, even though these dispersion type polycarboxylic acid water reducing agents for cement have better water reducing properties than the previous water reducing agents without a polyalkylene oxide group, their slump loss preventing effect is still not adequate.
On the other hand, together with progress in concrete technology, the requirements for the slump loss preventing effect in concrete also increased and the development of the slump maintaining type of polycarboxylic acids progressed. E.g., copolymers of polyethylene glycol methacrylate and methacrylic acid (refer for example to Document 5); copolymers selected from polyalkylene glycol diester monomers having unsaturated bonds, acrylate monomers and polyalkylene glycol monoester monomers having unsaturated bonds (refer for example to Document 6); copolymers of methacrylic acid and polyethylene glycol methacrylate whose oxyethylene group has 1 to 10 and 11 to 100 different chain lengths (refer for example to Document 7); copolymers of polyoxyalkylene derivatives and maleic anhydrides (refer for example to Document 8); copolymers of polyoxyalkylene derivatives and maleic anhydrides (refer for example to Document 9); copolymers of alkenyl ethers and maleic anhydrides (refer for example to Document 10); copolymers of olefins having 2 to 8 carbon atoms and ethylenic unsaturated dicarboxylic acid anhydrides (refer for example to Document 11) and metal complexes of copolymers etc. of olefins having 2 to 8 carbon atoms and ethylenic unsaturated dicarboxylic acids and of polyacrylic acids (refer for example to Document 12) etc. have been proposed; and the slump loss preventing effect, which is insufficient with dispersion type water reducing agents, has been improved by using slump maintaining agents in combination with the dispersion type polycarboxylic acid water reducing agents mentioned above (refer for example to Document 13).
Many inventions, like those mentioned above, are effective for improving water reducing properties, dispersion properties and slump loss preventing properties by means of polycarboxylic acid water reducing agents.
Nowadays, however, attention at concrete work site is not focused on single properties such as water reducing properties, dispersion properties or slump maintaining properties; but what, in the end, is urgently needed is a cement additive for achieving excellent working properties and workability and for realizing excellent economical efficiency during the whole work process.
Development at present, however, has stopped at improving specific properties of cement compositions.
Document 1: JP-B-02-16264
Document 2: JP-B-03-36774
Document 3: JP-B-59-18338
Document 4: JP-B-02-7897
Document 5: JP-B-06-104585
Document 6: JP-A-05-238795
Document 7: JP-A-09-286645
Document 8: Japanese Patent No.2541218
Document 9: JP-A-07-215746
Document 10: JP-A-05-310458
Document 11: Japanese Patent No. 2933994
Document 12: JP-A-62-83344
Document 13: Japanese Patent No.2741631